How Earth works 2

Geology, Plate Tectonics, Volcanoes, Earthquakes

what do earthquake epicenters outline

plate boundaries

what does the map of earthquake epicenters around the world show?

not a random pattern. but lines of earthquake activity that define edges of tectonic plates

example of evidence of plate tectonics

deep earthquakes

what’s the depth of most earthquakes

less than 25km

depth of deep earthquakes

300-700km

what do deep earthquakes allow

detection of subducting plate location

hotspots

volcanism within a tectonic plate

what is hotspot caused by

rising of hot magma from mantle piercing through crust and creating volcanoes

hotspots characteristics

-source(uprising magma) is stationary but overlying plate moves

-volcanism is less explosive and characterized by lava flows than ash clouds

hotspot results

creating chain of volcanoes that can tell direction and velocity of plate movement

hotspot examples

hawaii, usa and yellowstone, usa

oceanic hotspots

intraplate volcanism created by stationary hotspot of moving tectonic plate

oceanic hotspot result

volcanic “island” chain

how we understand the earth

must think in terms of geologic time rather than human time

-thousands, millions, and billions of years

who and when was the concept of time introduced and what term did he introduce

James Hutton in 1788, Uniformitarianism

Uniformitarianidm

Natural laws are uniform through time

Actualism

rates of earth processes can vary